Detection of muons with a lead/scintillating-fiber calorimeter

Abstract We report on an experimental study of the signals from high-energy (5–225 GeV) muons traversing a 9.5 interaction lengths deep electromagnetic/hadronic calorimeter consisting of lead and scintillating plastic fibers, constructed at CERN in the framework of the LAA project. The muons lose on average between 2.6 GeV (at 5 GeV) and 8.8 GeV (at 225 GeV) in this process. This energy loss can be measured with a precision of a fraction of a GeV in most of the events. Accuracy in the energy loss measurements is important since the rms spread in the energy loss of muons traversing this calorimeter is not smaller than ∼6% at any energy. The nominal calibration constants, derived from the calorimeter response to electromagnetic showers, are found to be incorrect for the muon signals. On average, these calibration constants are between 40% (for low energy muons) and 15% (high energy) too high. The fiber bunches sticking out of the back plane of the calorimeter for readout purposes cause the muon signals to be position dependent. This can cause an anomalous enhancement of the muon signal of up to 35%. A moderate position resolution of ∼ 1 cm is sufficient to correct for this effect. The e/mip ratio was found to be 0.72±0.03.